Screen bar

ABSTRACT

A screen bar cage for a rotary crusher is disclosed in which the screen bars are specially shaped to accurate dimensions by being formed of rolled steel cut to length. The front impact-receiving surface of each bar is a flat plane, inclined relative to the radial of the machine. The trailing surface has an upper portion, which is generally parallel with the front surface, and a lower portion which is convergent with the front surface of the same bar, forming with the front surface of the following bar a slot having an upper portion for determining the size of the fragmented material to be passed, and a lower divergent portion for discharging the material. Spacing lugs, at spaced intervals along the screen bar, extend integrally between the lower portion of the trailing surface of one bar and the front surface of the following bar. These integral clips form an arch support which distributes any radially outward or downward thrust which may be imposed on one bar, among the bars on either side thereof.

United States Patent Primary Exuminer Donald (3 Kelly Attorney-Paul & Paul ABSTRACT: A screen bar cage for a rotary crusher is disclosed in which the screen bars are specially shaped to accurate dimensions by being formed of rolled steel cut to length. The front impact-receiving surface of each bar is a flat plane, inclined relative to the radial of the machine. The trailing surface has an upper portion, which is generally parallel with the front surface, and a lower portion which is convergent with the front surface of the same bar, fonning with the front surface of the following bar a slot having an upper portion for determining the size of the fragmented material to be passed, and a lower divergent portion for discharging the material. Spacing lugs, at spaced intervals along the screen bar, extend integrally between the lower portion of the trailing surface of one bar and the front surface of the following bar. These integral clips form an arch support which distributes any radially outward or downward thrust which may be imposed on one bar, among the bars on either side thereof.

PATENTEI] JUL 6 |97| INVENTOR. Ralph R. DeFeo M 1? W6,

ATTORNEYS.

SCREEN BAR Jan. 19, 1954, and assigned by mesne assignment to the assignee of the present application, a screen bar cage is disclosed in which the bars have a special cross-sectional configuration which provides not only size-determining slots for the fragmented material but also slots which are self-clearing, i.e., slots which do not become choked with crushed material.

' The screen bars described in the aforesaid U.S. Patent are made from castings, and in the assembly of the screen bar cage it is ordinarily necessary to insert shims here and there to convert from a loose cage full of noisy rattles to a reasonably tight quiet cage. Each screen bar in the aforesaid patent includes, as part of the casting, a plurality of spacer webs which project laterally in both directions from the main body of the bar and which, when the cage is completed and inserted in the rotary crusher, occupy a generally circumferential direction relative to the crusher rotor. The exposed outer face of each spacer web in the patent engages the correspondingly exposed outer face of the spacer web of an adjacent screen bar, and these engaging faces of the spacer webs are disposed along substantially radial lines relative to the center of rotation of the crusher. As a result, each screen bar is required to bear alone whatever downward or radially outward thrust is imposed on the bar as a result of being impacted by material struck and thrown by the hammers, and it not infrequently occurs that the bars will bend under the thrust imposed and in so doing will loosen some of the spacer shims which had been inserted to tighten the cage.

SUMMARY OF THE PRESENT INVENTION By the present invention, a substantial improvement is provided over the screen bar cage disclosed in the aforesaid U.S. Pat. No. 2,666,589. In the first place, the screen bars of the present application are produced from rolled steel cut to desired lengths. The steel, preferably manganese, is rolled to exact cross-sectional shape and dimension. As a result, when the bars are assembled into the cage, the cage is inherently tight and the insertion of shims is unnecessary.

A further and very important difference between the screen bar of the present application and that of the prior art patent is that in the present application the spacing clips or lugs which extend laterally from the sidewalls of the bars, extend all the way across the intervening passage, from the sidewall of one bar to the sidewall of the next adjacent bar. Each clip, in the preferred form, is secured, as by welding, to the sidewall of one bar only. The outer or exposed end of the clip abuts against the sidewall of the adjacent bar, and in so doing forms an archlike construction so that any downward or radially outward thrust or load imposed on one of the screen bars is distributed among the bars on both sides thereof, with the result that the bar does not bend under a radial thrust load of a magnitude which would have caused bending of the screen bar of the prior art patent.

A primary object of the present invention is therefore to provide an improved screen bar cage having all the benefits provided by the screen bar cage of U.S. Pat. No. 2,666,589 and in addition thereto having substantially improved strength against radially outward forces.

A further object is to provide a screen bar cage which is easier to install, both initially and at the time of replacement, due to greater accuracy in the cross-sectional and lineal dimensions of the bar.

A still further object is to provide a generally stronger, rattle-free cage construction which does not require shims, and which provides more accurately dimensioned slots for determining the maximum size of the crushed particles to be passed.

2 BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammaticend elevational view, partly in section, of a ring hammer type of rotary crusher showing a screen bar cage embodying the present invention;

FIG. 2 is an enlarged fragmentary view, in section, ofa portion of the screen bar cage of FIG. 1;

FIG. 3 is a plan view looking down along the line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a portion of a ring-type rotary crusher is illustrated having a rotor shaft 12 having mounted thereon a rotor 13 which carries ring hammers 14. The ring hammers 14 are connected to the rotor by pins 17 and 18 positioned in pairs around the periphery of the rotor. When the shaft 12 is rotated, the ring hammers 14 extend outwardly to the positions illustrated in FIG. 1 and sweep in close proximity to the breaker plate 15 and the screen cage 16. The material to be crushed is dropped into the crusher through the delivery chute opening 19 and is initially crushed against the breaker plate 15, and then further broken against the screen bars 50 of the screen cage 16 by the rotating ring hammers 14. Fragmented pieces, if small enough in size, pass through the slots 60 between the screen bars 50.

In the particular form of machine shown in FIG. 1, the delivery chute opening 19 is above the rotor and is offset from the center of the rotor so that the material to be fragmented drops down between the breaker plate 15 and therotor and into the path of the ring hammers 14. The breaker plate 15, and the screen bars 50 of the cage 16 extend the axial width of the machine, from one end to the other. Both ends of the machine are similar, and have a cradle 28 pivotally supported at its upper end on a shaft 29 and adjustably supported at its lower end by the adjusting mechanism 31. The adjusting mechanism 31 is mounted on the rotatable shaft 32 supported by the end walls of the housing. The breaker plate 15 is mounted on the upper end of the cradle 28 and extends generally vertically from the lower edge of the opening 19 to below the horizontal centerline of the rotor.

The screen bars 50 of the screen cage 16 are mounted in the lower curved portion of the cradle 28, beginning from a point just below the horizontal line of the rotor. The screen bars run parallel to the rotor shaft 12 and transverse to the direction of movement of the ring hammers 14. The ends ofthe bars 50 are seated on the curved surface of the cradle 28 and are tightly held between the lower end surface of the breaker plate 15 and the crossmember 36 which interconnects the lower ends of the cradles. A reinforcing rod 37 extends across the machine from one cradle end to the other. A clamp 38 presses against the upper or radially inward end surface of the bars 50 to hold the bars on the cradle 28.

The screen bars 50 are spaced from each other by spacer clips 70 disposed at the ends of the bars 50 and also at spaced intervals along the bars forming, between the bars 50, slots 60 transverse to the direction of motion of the hammers 14. The spacer clips 70 between the bars 50 may be shorter in some cases, and longer in others, thereby to form narrower or wider slots 60, as is desired.

Each of the bars SO'has an upper surface 51 which faces the hammer circle and which receives the impact of any material thrown thereagainst by the rotating ring hammers 14. A front surface 52 of the bars'is plane and flat and angularly disposed, as seen best in FIG. 2, relative to the radial lines 112 which extends from the center axis of rotation of the rotor shaft 12. This surface 52 faces toward the rotating hammers, the direction of rotation being indicated by the arrow in FIG. 1. The opposite or trailing face of each screen bar 50 has an upper portion 53 which may be generally parallel with the leading face 52. The lower portion 54 of the trailing face is convergent relative to the leading face 52 thereby to form with the leading face 52 of the next adjacent bar a slot 60 having an upper portion 61 and a lower divergent portion 62. The upper portion 61 between the substantially parallel surfaces 53 and 52, determines the maximum size of fragmented material to be passed through that particular slot 60. The divergent lower portion 62 of the slot 60 functions to provide the 'nonclogging or self-clearing feature.

ln accordance with the present invention, each spacer clip 70 extends integrally across the divergent lower portion 62 of each slot 60 and is secured, as by welding, to the surface 54 of a bar 50, and abuts against the front surface 52 of an adjacent bar. There is such a spacer clip 70 at each end of the elongated bar 50 and a number of such spacer clips 70 at spaced inter' vals therealong, as is indicated in FIG. 3. While the spacer clips 70 in adjacent slots 60 are shown in FIG. 3 to be in alignment, they may occupy staggered positions.

The construction just described provides a significant and important advantage over the construction shown in US. Pat. No. 2,666,589, in that any downward or radially outward thrust or force imposed on the upper surface 5] of any one of the screen bars 50 is distributed to the adjacent bars on both sides thereof by transmission laterally through the spacer clips 70. Thus, the downward or radially outward load is distributed among several bars, and downward or radially outward bending of a bar 50 is avoided for loads or thrusts of a magnitude sufficient in the case of the screen bar structure shown in U.S. Pat. No. 2,666,589 to have caused such bending.

In addition to the advantages already mentioned, the rolled screen bars 50 of the present application are considerably cheaper to produce than are the cast screen bars of the prior art. As already indicated, the new bars 50 are of manganese steel, preferably Hatfield manganese. The spacer clips 70 are preferably of mild steel, and are welded to the lower portion of the trailing surface of the bar and of such desired lengths that when the clips abut against the front surface of the following screen bar, the desired spacing and width of slot is accurately obtained, the degree of accuracy being much greater than when the bars and webs are cast as in the prior art patent.

What I claim is:.

1. In a rotary crusher of the type having hammers moving in Y a hammer circle,

a. a screen bar cage mounted outside said hammer circle and comprising a plurality of screen bars spaced apart and forming therebetween slots for passing fragmentized material thercthrough;

b. each of said screen bars having an impact-receiving sur face facing upwardly toward said hammer circle, a front impact-receiving surface facing toward the moving hammers and inclined relative to the radial from the center axis of rotation of the hammer rotor, and a trailing surface on the opposite side of said bar from said front surface;

. said trailing surface having an upper portion generally parallel to said front surface forming therebetween an upper slot portion for determining the maximum size of fragmented material to be passed therethrough;

d. said trailing surface having a lower portion convergent relative to said front surface of the same screen bar forming with the front surface of the adjacent screen bar a divergent lower slot portion for discharging fragmented material passing through said size-determining upper slot portion;

e, spacing clips at spaced intervals along the length of said bars and extending integrally between the lower portion of said trailing surface of one bar and the radially inclined front surface of an adjacent bar and secured to at least one of said surfaces, forming therebetween an arch support for supporting said screen bars against radially outward forces imposed thereon.

2. Apparatus according to claim 1 characterized in that the spacing clips are welded to said lower portion of said trailing surface.

3. Apparatus according to claim 2 characterized in that said screenbars are produced from cut lengths of rolled steel bar. 

1. In a rotary crusher of the type having hammers moving in a hammer circle, a. a screen bar cage mounted outside said hammer circle and comprising a plurality of screen bars spaced apart and forming therebetween slots for passing fragmentized material therethrough; b. each of said screen bars having an impact-receiving surface facing upwardly toward said hammer circle, a front impactreceiving surface facing toward the moving hammers and inclined relative to the radial from the center axis of rotation of the hammer rotor, and a trailing surface on the opposite side of said bar from said front surface; c. said trailing surface having an upper portion generally parallel to said front surface forming therebetween an upper slot portion for determining the maximum size of fragmented material to be passed therethrough; d. said trailing surface having a lower portion convergent relative to said front surface of the same screen bar forming with the front surface of the adjacent screen bar a divergent lower slot portion for discharging fragmented material passing through said size-determining upper slot portion; e. spacing clips at spaced intervals along the length of said bars and extending integrally between the lower portion of said trailing surface of one bar and the radially inclined front surface of an adjacent bar and secured to at least one of said surfaces, forming therebetween an arch support for supporting said screen bars against radially outward forces imposed thereon.
 2. Apparatus according to claim 1 characterized in that the spacing clips are welded to said lower portion of said trailing surface.
 3. Apparatus according to claim 2 characterized in that said screen bars are produced from cut lengths of rolled steel bar. 